Method to Manufacture an Electronic Device for a Rubber Article

ABSTRACT

A method to manufacture an electronic device to be applied to rubber article. The device comprises an electronic element, two layers of thermoplastic material which are arranged in a sandwich-like manner so as to contain, between one another, the electronic element, and at least an outer rubber layer arranged to cover an outer surface of at least one of the respective thermoplastic layers. The method comprises a preliminary step comprising (a) a deposition operation, during which an adhesive solution consisting of a basic water solution comprising a latex of an elastomer rubber and a combination of resorcinol and formaldehyde is applied on at least one outer surface of one of the layers of thermoplastic material; and (b) a heating operation, during which the layers of thermoplastic material on which the adhesive solution was applied are kept at a temperature ranging from 120 to 230° C. for an amount of time ranging from 2 to 15 min.

The invention relates to a method to manufacture an electronic device tobe used in rubber articles.

In particular, the invention refers to a patch radio-frequencyidentification (RFID) device for tire applications, to which thedescription will explicitly refer without loss of generality.

In the tire industry, manufacturers have expressed the need forsolutions that allow for an automated and unequivocal identification oftires during their production, their use and their disposal.

For example, with specific reference to the production of tires, theautomated and unequivocal identification of the tires can allowmanufacturers to optimize production processes and logistics operations,support the use of automated control systems, carry out an efficientlocalization/tracking of the tires and, hence, build smart tirefactories.

The solution involving the use of barcodes applied on the tires, despiteallowing manufacturers to handle the production of tires and theproduction history of the single tires, is however affected by a seriesof drawbacks concerning the recording of a limited number of items ofinformation, the reading of the codes one by one with a given line ofsight and the risk of the codes being cancelled or damaged during theproduction and/or the normal operation/use of the tires, thus becomingunreadable or, anyway, difficult to read.

An alternative to the use of barcodes involves a patch radio-frequencyidentification (RFID) device for tires. This device consists of amulti-layer planar, flexible structure, which substantially comprisestwo insulating layers made of PET, which are arranged in a sandwich-likemanner so as to contain, between one another, an RFID chip, a firstantenna connected to the chip and, at least partially, a second antennaelectromagnetically coupled to the first antenna, and two outer rubberlayers, each arranged so as to cover an outer surface of a respectiveinsulating layer.

For insulating material like PET we mean “a lossless material with lowrelative permittivity and low electrical conductivity”.

Experiments have shown that this solution has a critical pointconcerning the adhesion between the insulating layers and the respectiverubber layer with which they are in contact.

As a person skilled in the art can immediately understand, if theinsulating PET layers, which enclose the antennas and the chip, are notcorrectly adhered to the two outer rubber layers, the RFID and thesurrounding rubber of the tire layers can be damaged. In particular,there can be a splitting up of the device, that necessarily jeopardizesthe correct operation of the device and can cause possible damages tothe rubber layer where the device is housed.

Indeed, if the insulating layers come out of the device due to thefailed adhesion with the outer rubber layers, they can make cuts andcracks in the surrounding rubber of the tire.

Basically, the same technical problem can be met in many otherelectronic devices to be inserted in a tire, of which the RFID is justan example. Other electronic devices could be generic sensors used intire applications like temperature sensors, pressure sensors or evenenergy harvesters.

Therefore, there is the need to have a solution that ensures a correctstructural stability of the electronic device to be applied in a tire.

The inventors of this invention conceived a method capable of fulfillingthe aforesaid need.

The subject-matter of the invention is a method to manufacture anelectronic device to be applied to rubber article; said devicecomprising an electronic element, two layers of thermoplastic materialwhich are arranged in a sandwich-like manner so as to contain, betweenone another, said electronic element, and at least an outer rubber layerarranged to cover an outer surface of at least one of the thermoplasticlayers; said method being characterized by comprising a preliminary stepcomprising (a) a deposition operation, during which an adhesive solutionconsisting of a basic water solution comprising a latex of an elastomerrubber and a combination of resorcinol and formaldehyde is applied on atleast one outer surface of one of the layers of thermoplastic material;and (b) a heating operation, during which the layers of thermoplasticmaterial on which the adhesive solution was applied are kept at atemperature ranging from 120 to 230° C. for an amount of time rangingfrom 2 to 15 min.

Preferably, at least one of the layers of thermoplastic material is madeof insulating material.

Preferably, said insulating material is chosen in the in the groupcomprising polyesters, polyamides, polyimides.

Preferably, said insulating material is comprised in the groupconsisting of PET, Nylon and polyethylene naphtalate.

Preferably, said rubber article is a tire.

Preferably, said electronic element comprises an RFID chip, a firstantenna connected to the chip and a second antenna electromagneticallycoupled to the first antenna.

Said basic water solution preferably comprises a pre-condensed resinconsisting of resorcinol and formaldehyde with isocyanate blockinggroups.

Said basic water solution preferably comprises lignin and a chemicalchosen between urea and thiourea.

Said elastomer rubber latex preferably comprises a latex ofstirene-butadiene-vinylpyridine or a latex of a mixture ofstirene-butadiene-vinylpyridine and stirene-butadiene.

Said deposition operation preferably involves said adhesive solutionbeing applied on both surfaces of the layers of thermoplastic material.

A further subject-matter of the invention is an electronic device to beused in rubber article characterized by being realized by the methodaccording to method of the present invention.

The invention will be best understood upon perusal of the followingdescription of an explanatory and non-limiting embodiment, withreference to the accompanying FIGURE, which shows the radio-frequencyidentification device in an exploded view.

In the FIGURE, number 1 indicates, as a whole, a radio-frequencyidentification (RFID) device according to the invention.

The device 1 comprises a transceiver assembly 2, two PET layers 3arranged in a sandwich-like manner on opposite sides of the transceiverassembly 2 and two outer rubber layers 4, each arranged on a respectiveouter surface 3 a of a PET layer 3. The transceiver assembly 2 comprisesan RFID chip 5, a first antenna 6 connected to the RFID chip 5 and asecond antenna 7 electromagnetically coupled to the first antenna 6.

Two radio-frequency identification (RFID) devices of the type shown inthe FIGURE were manufactured. The two devices are different from oneanother only because one of them was manufactured by depositing anadhesive solution according to the invention on an outer surface 3 a ofeach PET layer 3.

The adhesive solution was applied on the surface 3 a by means of a brush(deposition operation).

Table I shows the composition, in parts by weight, of the adhesivesolution used.

TABLE I Latex stirene-butadiene-vinylpyridine 72.7 Resorcinol 5.0Formaldehyde 2.3 Methylene diphenyl diisocyanate 20.0

After having applied the adhesive solution (deposition operation), thetwo PET layers 3 were subjected to a heating operation. The heatingoperation involved keeping the two PET layers 3 on which the adhesivesolution was applied in an oven at 220° C. for an amount of time of 3minutes.

Unlike what described above, according to a further embodiment of theinvention, the adhesive solution comprises a pre-condensed resinconsisting of resorcinol and formaldehyde with isocyanate blockinggroups, lignin and a chemical chosen between urea and thiourea. Thisadhesive solution offers the advantage of not having to use formaldehydein a free form.

After having carried out the preliminary step described above, theprocess goes on with a first step, in which the transceiver assembly 2is housed between the two PET layers 3, and, subsequently, with a secondstep, in which the two PET layers 3 are covered on the outside with tworespective layers 4 of non-vulcanized rubber.

Alternatively, the two PET layers 3 can be covered on the outside withtwo respective layers 4 of partially or totally vulcanized rubber.

By so doing, a first RFID device was manufactured.

The second RFID device was manufactured repeating the method describedabove with the sole exception of not having carried out the preliminarystep. In other words, in the manufacturing process of the second RFIDdevice, the first step was carried out using the PET layers 3 withouthaving applied the adhesive solution on them.

Unlike what described above, according to a preferred embodiment of theinvention, the adhesive solution can be applied on both surfaces of thePET layers 3.

In use, the RFID devices described above are included in a green rubberportion of a tire.

Alternatively, the RFID devices described above can be applied on acured rubber portion of a tire.

Once the RFID device has been inserted inside the tire, thevulcanization step is carried out. By so doing, the rubber layers of theRFID device, during the vulcanization, are cross-linked with thesurrounding rubber, ensuring the stability of the position of thedevice.

The first and the second RFID devices were subjected to an adhesion testaccording to ASTM D1876 method. Said test measures the adhesion forcebetween each one of the PET layers 3 and the respective rubber layer 4arranged so as to cover the outer surface 3 a.

Table II shows the values obtained with the aforesaid test.

TABLE II First RFID device Second RFID device Adhesion force 6.73 0.37(N/mm)

The values shown in Table II clearly prove that the method of theinvention can ensure a strong adhesion between the PET layer 3 and therespective rubber layer 4, thus avoiding a splitting up of the deviceand the problems caused by it.

Two other radio-frequency identification (RFID) devices (the third andthe fourth RFID devices) of the type shown in the FIGURE weremanufactured. The third and the fourth RFID devices differ from thefirst and the second RFID devices because they comprise layer 3 made ofNylon and not PET.

In addition, the third and the fourth RFID devices differ from eachother in the conditions used in the heating operation (b).

In particular,

-   -   for the third RFID device, the adhesive solution of table I was        applied on the surface 3 a of the Nylon layer by means of a        brush (deposition operation).

After having applied the adhesive solution (deposition operation), thetwo Nylon layers 3 were subjected to a heating operation. The heatingoperation involved keeping the two Nylon layers 3 on which the adhesivesolution was applied in an oven at 220° C. for an amount of time of 5minutes.

-   -   for the fourth RFID device, the adhesive solution of table I was        applied on the surface 3 a of the Nylon layer by means of a        brush (deposition operation).

After having applied the adhesive solution (deposition operation), thetwo Nylon layers 3 were subjected to a heating operation. The heatingoperation involved keeping the two Nylon layers 3 on which the adhesivesolution was applied in an oven at 155° C. for an amount of time of 10minutes.

For the first, third and fourth RFID devices the same amount of adhesivesolution was applied on the respective surfaces 3 a.

The third and the fourth RFID devices were subjected to an adhesion testaccording to ASTM D1876 method for measuring the adhesion force betweeneach one of the Nylon layers 3 and the respective rubber layer 4arranged so as to cover the outer surface 3 a.

Table III shows the values obtained with the aforesaid test.

TABLE III Third RFID device Fourth RFID device Adhesion force 6.9 7.9(N/mm)

Also the values shown in Table III clearly prove that the method of theinvention can ensure a strong adhesion between the Nylon layer 3 and therespective rubber layer 4, thus avoiding a splitting up of the deviceand the problems caused by it.

As stated above, the present invention adapts to any electronic deviceto be applied to a rubber article, e.g. a tire.

Depending on the electronic device, only one rubber layer 4 can be used.

1-12. (canceled)
 13. A method to manufacture an electronic device to beapplied to a rubber article, wherein the device comprises an electronicelement, two layers of thermoplastic material which are arranged in asandwich like manner so as to contain said electronic element therebetween, and at least an outer rubber layer arranged to cover an outersurface of at least one of the thermoplastic layers, said methodcomprising: a deposition operation, during which an adhesive solutioncomprising a basic water solution comprising a latex of an elastomerrubber and a combination of resorcinol and formaldehyde is applied on atleast one outer surface of one of the layers of thermoplastic material;and a heating operation, during which the layers of thermoplasticmaterial on which the adhesive solution was applied are kept at atemperature ranging from 120 to 230° C. for an amount of time rangingfrom 2 to 15 min.
 14. The method of claim 13, wherein at least one ofthe layers of thermoplastic material is made of insulating material. 15.The method of claim 14, wherein said insulating material is chosen in agroup comprising polyesters, polyamides, and polyimides.
 16. The methodof claim 14, wherein said insulating material is comprised in a groupconsisting of PET, Nylon, and polyethylene naphtalate.
 17. The method ofclaim 13, wherein said basic water solution comprises a pre-condensedresin comprising resorcinol and formaldehyde with isocyanate blockinggroups.
 18. The method of claim 17, wherein said basic water solutioncomprises lignin and a chemical chosen between urea and thiourea. 19.The method of claim 13, wherein said elastomer rubber latex comprises alatex of styrene-butadiene-vinylpyridine or a mixture ofstyrene-butadiene-vinylpyridine and styrene-butadiene.
 20. The method ofclaim 13, wherein said deposition operation involves said adhesivesolution being applied on both surfaces of the layers of thermoplasticmaterial.
 21. The method of claim 13, wherein said rubber article is atire.
 22. The method of claim 13, wherein said electronic elementcomprises an RFID chip, a first antenna connected to the chip, and asecond antenna electromagnetically coupled to the first antenna.
 23. Anelectronic device to be used in a rubber article, wherein the devicecomprises: an electronic element; two layers of thermoplastic materialwhich are arranged in a sandwich like manner so as to contain saidelectronic element there between; at least an outer rubber layerarranged to cover an outer surface of at least one of the thermoplasticlayers; and an adhesive solution comprising a basic water solutioncomprising a latex of an elastomer rubber and a combination ofresorcinol and formaldehyde applied on at least one outer surface of oneof the layers of thermoplastic material, wherein the layers ofthermoplastic material on which the adhesive solution was applied arekept at a temperature ranging from 120 to 230° C. during a heatingoperation of manufacture of the electronic device for an amount of timeranging from 2 to 15 min.
 24. The electronic device of claim 23, whereinthe electronic device is a radio-frequency identification (RFID) device.25. The electronic device of claim 24, wherein said electronic elementcomprises an RFID chip, a first antenna connected to the chip, and asecond antenna electromagnetically coupled to the first antenna.
 26. Theelectronic device of claim 23, wherein at least one of the layers ofthermoplastic material is made of insulating material.
 27. Theelectronic device of claim 26, wherein said insulating material ischosen in a group comprising polyesters, polyamides, and polyimides. 28.The electronic device of claim 27, wherein said insulating material iscomprised in a group consisting of PET, Nylon, and polyethylenenaphtalate.
 29. The electronic device of claim 23, wherein said basicwater solution comprises a pre-condensed resin comprising resorcinol andformaldehyde with isocyanate blocking groups.
 30. The electronic deviceof claim 29, wherein said basic water solution comprises lignin and achemical chosen between urea and thiourea.
 31. The electronic device ofclaim 23, wherein said elastomer rubber latex comprises a latex ofstyrene-butadiene-vinylpyridine or a mixture ofstyrene-butadiene-vinylpyridine and styrene-butadiene.
 32. Theelectronic device of claim 23, wherein said rubber article is a tire.